if I do it quickly right in front of my face, yeah, it's blurry, but that's not all motion blur does in games. Stretch your arm in front of you and move it side to side while looking at it, you can see all the details, your eyes follow the moving object, but in games, it blurs every single moving thing, even if you're looking at it. Same thing if someone is running on the other side of the street, you should have no problem focusing on said person while artificial motion blur would make it look terrible.